Honestly, Zeds kit is over balanced right now in a lot of ways. But I think perhaps the most frustrating thing about him, is that he is the only champion in league of legends in which I find myself in a situation, with nearly EVERY champion in mid where I think "Either I rush Zhonya's or at 6, I'm easy pickings" correct me if I'm wrong but shouldn't a champion have more counter play than buy X item or die?
I would figure Kat or Akali would cause more of that mindset than Zed.
With Zed, you know what he's trying to do. You know he's trying to whittle you down.
You know when he hits six he's going to try for you.
Why not freeze at tower range and cs while dealing a little harass now and then?
Why not make sure when he dives, you're under tower and have your CC ready so that when he appears you can just lock him down and let the turret do the work for you?
Or you could just give him a big middle finger 
